Another senior Republican, John McCain, said there were "no excuses for Trump's offensive and demeaning comments".

Trump, in the video, talks about attempts to woo a married woman and brags about how he "can do anything" to women.

"You know I'm automatically attracted to beautiful [women] ... I just start kissing them. It's like a magnet. Just kiss. I don't even wait," Trump said.

"And when you're a start they let you do it. You can do anything. Grab them by the p***y. You can do anything."

The billionaire also details his attempts to try and sleep with a married woman.

"You know I moved on her actually ... I moved on her and I failed. I'll admit it. I did try and f**k her. She was married."

"I took her out furniture ... I moved on her like a b***h, but I couldn't get there, and she was married. Then all of a sudden I see her, she's now got the big phony tits and everything. She's totally changed her look."

Trump has now issued a statement apologising for his comments.

"This was locker room banter, a private conversation that took place many years ago. Former President Bill Clinton has said far worse to me on the golf course -- not even close," the statement said. "I apologise if anyone was offended."

"I am sickened by what I heard today (Friday). Women are to be championed and revered, not objectified. I hope Trump treats this situation with the seriousness it deserves and works to demonstrate to the country that he has greater respect for women than this clip suggests," Ryan said.

"In the meantime, he is no longer attending tomorrow's (Saturday's) event in Wisconsin."

In an interview with Las Vegas television station KSNV-TV, Trump said his comments were made for "entertainment".

"A lot of that was done for the purpose of entertainment. There's nobody that has more respect for women than I do," he said.

Trump's Democratic rival Hillary Clinton has condemned his comments by describing them "horrific", saying on Twitter: "We cannot allow this man to become the US President."

Trump has recently opened up a new line of attack against Clinton -- her marriage to Bill Clinton and his infidelities -- despite Trump himself having a very public affair with his eventual second wife Marla Maples, while still married to his first wife Ivana Trump.

"Clinton was married to the single greatest abuser of women in the history of politics," Trump told the New York Times in a recent interview.

"Hillary was an enabler, and she attacked the women who Bill mistreated afterwards. I think it's a serious problem for them, and it's something that I'm considering talking about more in the near future."

The video has emerged two days before Trump takes part in the second presidential debate with Clinton.

The two candidates will be in St Louis for the televised encounter, with polling day only a month away.